High-temperature ductile alloys



United States Patent 3,395,013 HIGH-TEMPERATURE DUCTILE ALLOYS Sam Friedman, Great Neck, N.Y., assignor to General Telephone and Electronics Laboratories, Inc., a corporation of Delaware No Drawing. Filed Mar. 29, 1965, Ser. No. 443,690 9 Claims. (Cl. 75176) ABSTRACT OF THE DISCLOSURE A group of tungsten-base alloys containing between 1% and 10% rhenium, carbon and a reactive metal from the group consisting of hafnium, zirconium and titanium. These low rhenium-content alloys may be used to fabricate wrought forms having high strength at elevated temperatures, high recrystallization temperatures and low duetile-to-brittle transition temperatures.

This invention relates to tungsten base alloys characterized by high strength at elevated temperatures and low ductile-brittle transition temperatures.

The tungsten base alloys of the present invention contain rhenium, carbon and a reactive metal selected from Group IV-A of the Periodic Chart. As is well known, the addition of rhenium to tungsten produces alloys having reduced ductile-to-brittle transition temperatures. However, the scarcity and high cost of rhenium has limited the use of these materials for many applications such as sheet, tubing and other wrought forms.

Accordingly, it is an object of my invention to provide alloys which employ relatively small amounts of rhenium yet have low ductile-to-brittle transition temperatures, high strength at elevated temperatures and high recrystallization temperatures.

In the present invention, tungsten base alloys are provided which contain between 1% and 10% rhenium, 0.002% to 0.05% carbon and a reactive metal selected from the group consisting of hafnium, zirconium and titanium. The percentage of reactive metal in the alloy depends on the metal used, hafnium being present in an amount between 0.01% and 1.0%, zirconium 0.01% to 0.3% and titanium 0.03% to 0.3%. (All percentages given are by Weight.) By varying the constituents within the specified ranges the best combination of mechanical properties and ease of fabricability may be obtained for a given application. In particular, it has been found that a combination of high elevated temperature strength, high recrystallization temperatures and at least partial bend ductility at room temperature are found in the preferred compositions of Table I.

TABLE I Constituents: Weight percent Reactive metal- Hafnium 0.0l0.5 Zirconium 0.01-0.25 Titanium 0.060.25 Rhenium 3-10 Carbon 0.0020.02 Tungsten Balance 3,395,013 Patented July 30, 1968 These alloys compared with unalloyed tungsten made by the same process are generally stronger at 1650 C., have higher recrystallization temperatures and are duetile at lower temperatures. In particular, a number of the alloys in all three systems are completely ductile at room temperature or below. For example, the alloys of Table I exhibit ultimate tensile strength at 1650 C. in the range 35,000 p.s.i. to 67,000 p.s.i., as compared to 13,000 p.s.i. for unalloyed tungsten. The ductile-to-brittle transition occurs in the range from less than 50 C. to C. for the new alloys as compared to C. for unalloyed tungsten. The recrystallization temperature for unalloyed tungsten is between 1450 C. and 1500 C. whereas the present alloys have recrystallization temperatures in the range 1600 C. to 1850 C. The high strengths and high recrystallization temperatures obtained in these tungsten base alloys is believed due to the formation during fabrication of a uniformly dispersed reactive metal carbide having particle size predominantly in the range 50 to 1000 Angstroms.

EXAMPLE I Elemental powders of carbon, rhenium and tungsten were blended with hafnium hydride to form a uniform mixture which was then subjected to a pressure of approximately 50,000 pounds per square inch to form a billet. The billet was next sintered at a temperature of about 2350 C. for approximately 4 hours to mutually diffuse the different ingredients thereby forming a solid solution of hafnium and rhenium in tungsten, the carbon probably being partitioned between tungsten carbide and a solid solution of carbon in tungsten. The billet was then fabricated by forging at a temperature of approximately 1850 C. from 0.05 inch to 0.3 inch thick followed by rolling at a temperature of about 1550 C. to form sheets having a thickness of approximately 0.040 inch. During the fabrication process, carbon precipitates as a finely dispersed reactive metal carbide.

While a powder metallurgy process was used in forming the sheets, it shall be understood that the alloys may also be consolidated by other suitable processes such as vacuum arc-casting. Fabrication may be accomplished by other techniques such as extruding, forging or drawing .to produce the desired wrought form.

Measurements of ultimate tensile strength, recrystallization temperature and ductile-to-brittle transition temperature were carried out for a number of alloys. The recrystallization temperature was established by determining at what temperature the alloy must be heated for one hour before the fibrous structure completely disappears and recrystallization is essentially complete. The transition from ductile-to-brittle behavior, which occurs over a range of temperatures, was measured by attempting to bend specimens 1 inch long by inch wide by 0.04 inch thick over a radius four times the thickness of the sheet through a 105 angle at several temperatures and determining the minimum temperature at which the samle cracked after a small but perceptible amount of bending '(nil ductility temperature) and the minimum temperature at which the sample bent 105 without cracking (ductility temperature).

Characteristics of the alloys at diiierent compositions sisting essentially of from 3% to 10% rhenium, 0.002% are shown in Table II. A dash in the table indicates that to 0.02% carbon, from 0.01% to 0.5% of a reactive the listed property was not measured for that sample. metal selected from the group consisting of hafnium,

TABLE II Alloy Percent By Weight Ultimate Duetile-to-Brittle Transition One Hour Tensile Temp. C.) Reerystall. Strength at Temperature Hf Re C W 1,050 o. (p.s.i.) Nil Duet. Duetility 0.)

Temp. Temp.

EXAMPLE II zirconium and titanium, the balance consisting of tung- An alloy consisting of carbon, rhenium, zirconium and stem tungsten was prepared by the method described for the 20 A tungsten base alloy charactenzed by hlgh Strength alloy f Example I, bl 111 gives h characteristics f at elevated temperatures and a low ductile-to-brittle tranvarious compositions of this alloy. sition temperature in the range 5 0 C. to +125 C. con- TABLE III Alloy Percent By Weight Ultimate Duetile-to-Brittle Transition One Hour Tensile Temp. C.) Reerystall. Strength at Temperature Zr Re C W 1,650 C. (p.s.i.) Nil Duet. Ductility C.)

Temp. Temp.

0. 010 Bal 65,000 -30 1, 825-1, 850 0. 004 Bal 50 50 1, 800-1, 825 0. 015 Bal 03 000 0 014 Bal 63,000 0 023 Bal ,000 0. 005 Bal 00, 000 0 1, 750-1, 775 0. 01 Bal 59, 000 -10 1, 750-1, 775

EXAMPLE III sisting essentially of from 1% to 10% rhenium, 0.002% An alloy consisting of carbon, rhenium, titanium and to 095% f f from 0-01% to 10% hafmum the tungsten was prepared by the method of Example I. Table balance Consisting of tungsten- 1v gives the characteristics of various compositions of this A tungsten base alloy characterized y high strength alloy, at elevated temperatures and a low ductile-to-brittle tran- TABLE IV Alloy Percent By Weight Ultimate Duetile-to-Brittle Transition One Hour Tensile Temp. C.) Reerystall. Strength at Temperature Ti Re 0 W 1,050 o. (p.s.i.) Nil Duet. Duetility 0.)

Temp. Temp.

From these results it is apparent that the new alloys sition temperature in the range C. to +125 C. conexhibit high strength at elevated temperatures and are sisting essentially of from 1% to 10% rhenium, 0.002%

ductile at low temperatures. The alloys also have high to 0.05% carbon, from 0.01% to 0.3% zirconium, the recrystallization temperatures as compared to unalloyed balance consisting of tungsten. tungsten. For applications Where a high melting point is 5. A tungsten base alloy characterized by high strength desired, the composition containing the minimum alloying at elevated temperatures and a low ductile-to-brittle traningredients consistent with desired mechanical properties sition temperature in the range 50 C. to +125 C. conhave been found most suitable. 0 sisting essentially of from 1% to 10% rhenium, 0.002% As many changes could be made in the above described to 0.05% carbon, from 0.03 to 0.3 titanium, the compositions it is intended that all matter contained balance consisting of tungsten. therein shall be interpreted as illustrative and not in a 6. A tungsten base alloy characterized by high strength limiting sense. at elevated temperatures and a low ductile-to-brittle tran- What is claimed is: 35 sition temperature in the range 50 C. to +125 C. con- 1. A tungsten base alloy characterized by high strength sisting essentially of from 3% to 10% rhenium, 0.002% at elevated temperatures and a low duotile-to-brittle tranto 0.02% carbon, from 0.05 to 0.5 hafnium, the sition temperature in the range -50 C. to +125 C. conbalance consisting of tungsten. sisting essentially of from 1% to 10% rhenium, 0.002% 7. A tungsten base alloy characterized by high strength to 0.05 carbon, from 0.01% to 1.0% of a reactive metal at elevated temperatures and a low ductile-to-brittle transelected from the group consisting of hafnium, zirconium sition temperature in the range 50 C. to +125 C. conand titanium, the balance consisting of tungsten. sisting essentially of from 3% to 10% rhenium, 0.002% 2. A tungsten base alloy characterized by high strength to 0.02% carbon, from 0.01% to 0.25% zirconium, the at elevated temperatures and a low ductile-to-brittle tranbalance consisting of tungsten.

sition temperature in the range 50 C. to +125 C. eon- 8. A tungsten base alloy characterized by high strength at elevated temperatures and a lOw ductile-to-brittle transition temperature in the range 50 C. to +125 C. consisting essentially of from 3% to 10% rhenium, 0.002% to 0.02% carbon, from 0.06% to 0.25% titanium, the balance consisting of tungsten.

9. A tungsten base alloy characterized by high strength at elevated temperatures and a low ductile-to-brittle tran sition temperature in the range -50 C. to +125 C. consisting essentially of from 1% to 10% rhenium, 0.002% to 0.05% carbon, 0.01% to 1.0% of a reactive metal selected from the group consisting of hafnium, zirconium and titanium, the balance consisting of tungsten, said alloy containing uniformly dispersed particles of reactive metal carbide having particle sizes predominantly in the range 50 to 1000 Angstroms.

6 References Cited UNITED STATES PATENTS 3,116,145 12/1963 Semchyshen 75-476 3,236,699 2/1966 Pugh et a1 75-176 3,243,291 3/ 1966 Dickinson et al 75-176 OTHER REFERENCES "Nb, Ta, Mo and W, Quarrell, Elsevier Publishing Co.,

10 New York, 1961, pp. 321 and 347-361 relied on.

Field, et al., Research and Development of Tantalum and Tungsten Base Alloys, July 6, 1961, pp. 81-84 and 121-124 relied on.

15 CHARLES N. LOVELL, Primary Examiner. 

